Problem: A goblet contains $3$ red marbles, $11$ green marbles, and $4$ blue marbles. If a marble is randomly chosen, what is the probability that it is blue?
Answer: There are $3 + 11 + 4 = 18$ marbles in the goblet. There are $4$ blue marbles. The probability is $ \frac{4}{18} = \dfrac{2}{9}$.